Implantable medical device for providing stimulation therapy

ABSTRACT

An electrical stimulation system provides stimulation therapy to a patient. The system includes a neurostimulation lead that contacts patient tissue and couples with an implantable stimulation device, such as an implantable pulse generator, that receives stimulation parameters for providing stimulation therapy to a patient. The implantable stimulation device includes a header with a plurality of connector assemblies that receive an end of the neurostimulation lead, and a case containing a charging coil and a telemetry coil coupled to programming circuitry on a printed circuit board, which is in turn coupled to the connector assemblies via a feedthrough assembly. The telemetry coil receives data from an external programmer and transmits the data to the programming circuitry, which in turn uses the data to communicate to the connector assemblies and the neurostimulation lead to provide stimulation therapy to a patient.

RELATED APPLICATION DATA

The present application claims the benefit under 35 U.S.C. §119 to U.S.provisional patent application Ser. No. 61/446,438, filed Feb. 24, 2011.The foregoing application is hereby incorporated by reference into thepresent application in its entirety.

FIELD OF THE INVENTION

The present invention relates to implantable medical devices, and moreparticularly, to devices and methods for providing stimulation therapyto patients.

BACKGROUND OF THE INVENTION

Implantable stimulation devices generate and deliver electrical stimulito bodily nerves and tissues for the therapy of various biologicaldisorders, such as: pacemakers to treat cardiac arrhythmia;defibrillators to treat cardiac fibrillation; cochlear stimulators totreat deafness; retinal stimulators to treat blindness; musclestimulators to produce coordinated limb movement; spinal cordstimulators to treat chronic pain; cortical and deep brain stimulatorsto treat motor and psychological disorders; and other neural stimulatorsto treat urinary incontinence, sleep apnea, shoulder sublaxation, etc.The present invention may find applicability in all such applications,although the description that follows will generally focus on the use ofthe invention within a spinal cord stimulation system, such as thatdisclosed in U.S. Pat. No. 6,516,227, issued Feb. 4, 2003 in the name ofinventors Paul Meadows et al., which is incorporated herein by referencein its entirety.

Typical implantable stimulation devices include a neurostimulator, oneor more leads electrically coupled to the neurostimulator, and an arrayof stimulator electrodes on each lead. The stimulator electrodes are incontact with or near the bodily tissue to be stimulated. A pulsegenerator in the neurostimulator generates electrical pulses that aredelivered by the electrodes to bodily tissue. The neurostimulatortypically includes an implantable rounded case having circuitry such asa printed circuit board, a telemetry coil for communicating with anexternal programmer to control the electrical pulses, and a chargingcoil for charging the neurostimulator.

The neurostimulator also includes a header having one or more connectorassemblies for receiving the leads, wherein the connector assemblieshave one or more connector contacts for coupling to the leads. In commonmodels of such neurostimulators, there are two connector assemblies inthe header, each having eight contacts. However, to allow for greaterrange in stimulation parameters, it is desirable for the header toinclude more electrode contacts for coupling to the lead, for example,thirty-two contacts. At the same time, it is preferred to keep the caseand header as small as possible and to maintain a curved configurationfor patient comfort. Therefore, a proper neurostimulator design toaccommodate thirty-two electrodes, without affecting device performance,is desirable.

It is also common for neurostimulators to house a telemetry coil in theheader. However, this requires a feedthrough to couple the telemetrycoil to resonant circuit components and transceiver circuitry in thecase. This can add to the complexity of the device and lead to problemswith hermeticity. Additionally, the feedthroughs require significantextra steps during manufacture, thus allowing for greater error andquality concerns.

Another disadvantage of having the telemetry coil in the header is thatthe coil and the feedthroughs connected to the coil take up space in theheader, which may be limited based on the complexity of the stimulationsystem. At the same time, it is desirable to make stimulation devicessmaller for patient comfort. Moreover, while previous neurostimulatorshad eight or sixteen contacts for coupling to the electrode leads, newerdesigns may include thirty-two or more contacts, further limiting spacein the header.

Thus, there remains a need for improved stimulation devices and methodsthat optimize performance with an increased number of electrodes andselective positioning of the telemetry coil, while also having a small,rounded configuration for patient comfort that does not compromisedevice performance.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a tissuestimulation system is provided. The stimulation system has at least oneimplantable neurostimulation lead and an implantable neurostimulator.The neurostimulator includes at least one connector assembly configuredfor respectively receiving the at least one neurostimulation lead, acase, a circuit board positioned in the case, a telemetry coilpositioned in the case that is electrically coupled to the circuit boardand spaced a distance away from the circuit board, and a charging coilpositioned in the case that is electrically coupled to the circuitboard. In one embodiment, the telemetry coil is positioned on a spacerthat spaces the telemetry coil the distance away from the circuit board.In a further embodiment, a plurality of pins are affixed to the spacer,wherein at least one of the pins electrically couples the telemetry coilto the circuit board, and at least one of the pins mechanically couplesthe telemetry coil to the circuit board.

In a second aspect of the present invention, an implantableneurostimulator is provided. The neurostimulator has a case, a circuitboard positioned in the case, a telemetry coil positioned in the casethat is electrically coupled to the circuit board and spaced a distanceaway from the circuit board, and a charging coil positioned in the casethat is electrically coupled to the circuit board. In one embodiment,the telemetry coil is positioned on a spacer that spaces the telemetrycoil the distance away from the circuit board. In a further embodiment,a plurality of pins are affixed to the spacer, wherein at least one ofthe pins electrically couples the telemetry coil to the circuit board,and at least one of the pins mechanically couples the telemetry coil tothe circuit board.

In a third aspect of the present invention, a tissue stimulation systemis provided that includes at least one implantable neurostimulation leadand an implantable neurostimulator. The neurostimulator has a headerwith at least one connector assembly configured for respectivelyreceiving the at least one neurostimulation lead, a circuit board havingprogramming circuitry, and a flex circuit coupled between the at leastone connector assembly and the circuit board. In one embodiment, thesystem includes a feedthrough assembly with a plurality of pins coupledto the flex circuit that electrically couple the flex circuit to the atleast one connector assembly. In another embodiment, one or more of theplurality of pins traverse through one or more holes in the flexcircuit. In another embodiment, the feedthrough assembly has a metalflange forming a well containing an insulative material, and the pinsextend from the flex circuit through the insulative material. In yetanother embodiment, the at least one connector assembly has a pluralityof connector contacts for electrically coupling with theneurostimulation lead, and the pins are electrically coupled to theconnector contacts.

In a fourth aspect of the present invention, an implantableneurostimulator is provided. The neurostimulator has at least oneconnector assembly configured for receiving at least oneneurostimulation lead, a circuit board having programming circuitry, anda flex circuit coupled between the at least one connector assembly andthe circuit board. In one embodiment, the system includes a feedthroughassembly with a plurality of pins coupled to the flex circuit thatelectrically couple the flex circuit to the at least one connectorassembly. In another embodiment, one or more of the plurality of pinstraverse through one or more holes in the flex circuit. In anotherembodiment, the feedthrough assembly has a metal flange forming a wellcontaining an insulative material, and the pins extend from the flexcircuit through the insulative material. In yet another embodiment, theat least one connector assembly has a plurality of connector contactsfor electrically coupling with the neurostimulation lead, and the pinsare electrically coupled to the connector contacts.

In a fifth aspect of the present invention, a tissue stimulation systemis provided that includes at least one implantable neurostimulation leadand an implantable neurostimulator. The neurostimulator has at least oneconnector assembly configured for respectively receiving the at leastone neurostimulation lead, a fastener configured for securing therespective one of the at least one neurostimulation leads in the atleast one connector assembly, and at least one septum, each having anouter block and an inner block framed within the outer block. Adjacentedges of the inner and outer blocks form at least one slot for receivinga tool for manipulating the fastener for securing the respective one ofthe at least one neurostimulation leads in the respective one of the atleast one connector assembly. In one embodiment, the neurostimulator hasa retainer in which the at least one connector assembly is positioned.In another embodiment, a connector block is coupled to each at least oneconnector assembly and has the fastener positioned therein. In anotherembodiment, the outer and inner blocks of the at least one septum arecomposed of silicone.

In yet another embodiment, the neurostimulator has a shell housing theat least one connector assembly, and the shell has a first transverseline and a second transverse line both aligned parallel to the at leastone connector assembly. The first transverse line extends between firstopposing ends of the shell, the second transverse line extends betweensecond opposing ends of the shell, and the first transverse line isshorter than the second transverse line. In a further embodiment, atleast one upper connector assembly longitudinally aligned along thefirst transverse line, and at least one lower connector assemblylongitudinally aligned along the second transverse line. In yet afurther embodiment, the neurostimulator has at least one upper strainrelief member longitudinally aligned along the first transverse line andextending between an end of the at least one upper connector assemblyand one of the first opposing ends of the shell, and at least one lowerstrain relief member longitudinally aligned along the second transverseline and extending between an end of the at least one lower connectorassembly and one of the second opposing ends of the shell. The at leastone upper strain relief member has a shorter length than the at leastone lower strain relief member.

In a sixth aspect of the present invention, an implantableneurostimulator is provided. The neurostimulator has at least oneconnector assembly configured for receiving a neurostimulation lead, afastener configured for securing the respective one of the at least oneneurostimulation leads in the at least one connector assembly, and atleast one septum, each having an outer block and an inner block framedwithin the outer block. Adjacent edges of the inner and outer blocksform at least one slot for receiving a tool for manipulating thefastener for securing the respective one of the at least oneneurostimulation leads in the respective one of the at least oneconnector assembly. In one embodiment, the neurostimulator has aretainer in which the at least one connector assembly is positioned. Inanother embodiment, a connector block is coupled to each at least oneconnector assembly and has the fastener positioned therein. In anotherembodiment, the outer and inner blocks of the at least one septum arecomposed of silicone.

In yet another embodiment, the neurostimulator has a shell housing theat least one connector assembly, and the shell has a first transverseline and a second transverse line both aligned parallel to the at leastone connector assembly. The first transverse line extends between firstopposing ends of the shell, the second transverse line extends betweensecond opposing ends of the shell, and the first transverse line isshorter than the second transverse line. In a further embodiment, atleast one upper connector assembly longitudinally aligned along thefirst transverse line, and at least one lower connector assemblylongitudinally aligned along the second transverse line. In yet afurther embodiment, the neurostimulator has at least one upper strainrelief member longitudinally aligned along the first transverse line andextending between an end of the at least one upper connector assemblyand one of the first opposing ends of the shell, and at least one lowerstrain relief member longitudinally aligned along the second transverseline and extending between an end of the at least one lower connectorassembly and one of the second opposing ends of the shell. The at leastone upper strain relief member has a shorter length than the at leastone lower strain relief member.

In a seventh aspect of the present invention, an implantableneurostimulator is provided. The neurostimulator has a connector headerconfigured for receiving a neurostimulation lead, a divot formed in eachof the opposing sides of the connector header, and a suture holeextending between the divots. In one embodiment, each divot has aplurality of side surfaces, and each side surface is angled less than 90degrees from an outer surface of the connector header. In anotherembodiment, each divot has a bottom surface, and a terminating end ofthe suture hole is positioned at the bottom surface.

In an eighth aspect of the invention, an implantable neurostimulator isprovided. The neurostimulator has a shell having a first transverse lineextending between first opposing ends of the shell, and a secondtransverse line extending between second opposing ends of the shell,wherein the first transverse line is shorter than the second transverseline. The neurostimulator also has at least one upper connector assemblyand at least one lower connector assembly housed in the shell, eachconfigured for receiving a neurostimulator lead, wherein the at leastone upper connector assembly is longitudinally aligned along the firsttransverse line, and the at least one lower connector assembly islongitudinally aligned along the second transverse line. Theneurostimulator also has at least one upper strain relief memberlongitudinally aligned along the first transverse line and extendingbetween an end of the at least one upper connector assembly and one ofthe first opposing ends of the shell, and at least one lower strainrelief member longitudinally aligned along the second transverse lineand extending between an end of the at least one lower connectorassembly and one of the second opposing ends of the shell. The at leastone upper strain relief member has a shorter length than the at leastone lower strain relief member.

In one embodiment, the at least one upper connector assembly and atleast one lower connector assembly has contacts for electricallycoupling to the respective electrode lead received therein. In anotherembodiment, the at least one upper connector assembly and at least onelower connector assembly are positioned in a retainer. In yet anotherembodiment, the neurostimulator has at least one upper connector blockadjacent the at least one upper connector assembly and at least onelower connector block adjacent the at least one lower connectorassembly. In yet another embodiment, each of the at least one upperconnector block and at least one lower connector block has a fastenerdisposed therein for securing the respective electrode received in theat least one upper connector assembly and the at least one lowerconnector assembly.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 is a plan view of one embodiment of a neurostimulation systemarranged in accordance with the present inventions;

FIG. 2 is a plan view of the neurostimulation system of FIG. 1 in usewith a patient;

FIG. 3 is a side view of a neurostimulator and electrode leads used inthe neurostimulation system of FIG. 1;

FIG. 4 is a perspective view of the neurostimulator of FIG. 3;

FIGS. 5 and 6 are cut-away views of opposing sides of theneurostimulator of FIG. 3;

FIG. 7 is a side view of a spacer and telemetry coil from theneurostimulator of FIG. 3;

FIG. 8 is a cross-section view of the spacer and telemetry coil of FIG.7;

FIGS. 9 and 10 are partial exploded view of connector assemblies in aretainer element from the neurostimulator of FIG. 3;

FIG. 10A is a perspective view of a septum featured in FIG. 9;

FIG. 10B is an exploded view of the septum of FIG. 10A;

FIG. 10C is a cross-sectional view of the septum of FIG. 10A taken alongthe line 100 and connector blocks featured in FIG. 9;

FIG. 11 is a perspective view of feedthrough pins coupled to theconnector assemblies from FIG. 9;

FIG. 12 is a perspective view of a feedthrough assembly with thefeedthrough pins from FIG. 11;

FIG. 13A is a perspective view of a flex circuit having holes forreceiving the feedthrough pins from FIGS. 11 and 12; and

FIG. 13B is a cross-sectional view of the flex circuit in FIG. 13A takenalong the line 13B.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The description that follows relates to a spinal cord stimulation (SCS)system. However, it is to be understood that the while the inventionlends itself well to applications in SCS, the invention, in its broadestaspects, may not be so limited. Rather, the invention may be used withany type of implantable electrical circuitry used to stimulate tissue.For example, the present invention may be used as part of a pacemaker, adefibrillator, a cochlear stimulator, a retinal stimulator, a stimulatorconfigured to produce coordinated limb movement, a cortical stimulator,a deep brain stimulator, peripheral nerve stimulator, microstimulator,or in any other neural stimulator configured to treat urinaryincontinence, sleep apnea, shoulder sublaxation, headache, etc.

Turning first to FIG. 1, an exemplary SCS system 10 generally includesone or more (in this case, two) implantable neurostimulation leads 12, aneurostimulator (i.e., an implantable pulse generator) (IPG) 14, anexternal remote controller RC 16, a clinician's programmer (CP) 18, anExternal Trial Stimulator (ETS) 20, and an external charger 22.

The IPG 14 is physically connected via one or more percutaneous leadextensions 24 to the neurostimulation leads 12, which carry a pluralityof electrodes 26 arranged in an array. In the illustrated embodiment,the neurostimulation leads 12 are percutaneous leads, and to this end,the electrodes 26 are arranged in-line along the neurostimulation leads12. In alternative embodiments, the electrodes 26 may be arranged in atwo-dimensional pattern on a single paddle lead. As will be described infurther detail below, the IPG 14 includes pulse generation circuitrythat delivers electrical stimulation energy in the form of a pulsedelectrical waveform (i.e., a temporal series of electrical pulses) tothe electrode array 26 in accordance with a set of stimulationparameters.

The ETS 20 may also be physically connected via the percutaneous leadextensions 24 and external cable 30 to the neurostimulation leads 12.The ETS 20, which has similar pulse generation circuitry as that of theIPG 14, also delivers electrical stimulation energy in the form of apulsed electrical waveform to the electrode array 26 in accordance witha set of stimulation parameters. The major difference between the ETS 20and the IPG 14 is that the ETS 20 is a non-implantable device that isused on a trial basis after the neurostimulation leads 12 have beenimplanted and prior to implantation of the IPG 14, to test theresponsiveness of the stimulation that is to be provided.

The RC 16 may be used to telemetrically control the ETS 20 via abi-directional inductive link 32. Once the IPG 14 and neurostimulationleads 12 are implanted, the RC 16 may also be used to telemetricallycontrol the IPG 14 via a bi-directional magnetic coupling link 34. Suchcontrol allows the IPG 14 to be turned on or off and to be programmedwith different stimulation parameter sets. The IPG 14 may also beoperated to modify the programmed stimulation parameters to activelycontrol the characteristics of the electrical stimulation energy outputby the IPG 14. It should be noted that rather than an IPG, the system 10may alternatively utilize an implantable receiver-stimulator (not shown)connected to the lead 12. In this case, the power source, e.g., abattery, for powering the implanted receiver, as well as controlcircuitry to command the receiver-stimulator, will be contained in anexternal controller/charger inductively coupled to thereceiver-stimulator via an electromagnetic link.

The CP 18 provides clinician detailed stimulation parameters forprogramming the IPG 14 and ETS 20 in the operating room and in follow-upsessions. The CP 18 may perform this function by indirectlycommunicating with the IPG 14 or ETS 20, through the RC 16, via an IRcommunications link 36. Alternatively, the CP 18 may directlycommunicate with the IPG 14 or ETS 20 via an RF communications link ormagnetic coupling link (not shown). The clinician detailed stimulationparameters provided by the CP 18 are also used to program the RC 16, sothat the stimulation parameters can be subsequently modified byoperation of the RC 16 in a stand-alone mode (i.e., without theassistance of the CP 18).

The external charger 22 is a portable device used to transcutaneouslycharge the IPG 14 via an inductive link 38. Once the IPG 14 has beenprogrammed, and its power source has been charged by the externalcharger 22 or otherwise replenished, the IPG 14 may function asprogrammed without the RC 16 or CP 18 being present.

For purposes of brevity, the details of the RC 16, CP 18, ETS 20, andexternal charger 22 will not be described herein. Details of exemplaryembodiments of these devices are disclosed in U.S. Pat. No. 6,895,280,which is expressly incorporated herein by reference.

As shown in FIG. 2, the electrode leads 12 are implanted within thespinal column 42 of a patient 40. The preferred placement of theneurostimulation leads 12 is adjacent, i.e., resting near, or upon thedura, adjacent to the spinal cord area to be stimulated. Due to the lackof space near the location where the electrode leads 12 exit the spinalcolumn 42, the IPG 14 is generally implanted in a surgically-made pocketeither in the abdomen or above the buttocks. The IPG 14 may, of course,also be implanted in other locations of the patient's body. The leadextension 24 facilitates locating the IPG 14 away from the exit point ofthe electrode leads 12. As there shown, the CP 18 communicates with theIPG 14 via the RC 16.

Referring now to FIG. 3, the external features of the neurostimulationleads 12 and the IPG 14 will be briefly described. In the illustratedembodiment, there are four stimulation leads 12(1)-12(4), whereinneurostimulation lead 12(1) has eight electrodes 26 (labeled E1-E8),neurostimulation lead 12(2) has eight electrodes 26 (labeled E9-E16),neurostimulation lead 12(3) has eight electrodes 26 (labeled E17-E24),and neurostimulation lead 12(4) has eight electrodes 26 (labeledE24-E32). The actual number and shape of leads and electrodes will, ofcourse, vary according to the intended application.

As shown in FIGS. 3 and 4, the IPG 14 comprises an outer case 44 forhousing the electronic and other components (described in further detailbelow), and a header portion 46 coupled to the case 44 for receiving theproximal ends of the neurostimulation leads 12(1)-12(4) for mating in amanner that electrically couples the electrodes 26 to the electronicswithin the case 44.

The outer case 44 is composed of an electrically conductive,biocompatible material, such as titanium 6-4, and forms a hermeticallysealed compartment wherein the internal electronics are protected fromthe body tissue and fluids. In the illustrated embodiment, the case 44has a rounded configuration with a maximum circular diameter D of about50 mm, and preferably about 45 mm, and a maximum thickness W of about 10mm, and preferably about 8 mm. The case 44 is formed using any suitableprocess, such as casting, molding, and the like. The header 46 has arounded configuration that corresponds with that of the case 44, suchthat the case 44 and the header 46 together form a rounded body.

As will be described in further detail below, the IPG 14 includes pulsegeneration circuitry 48 (see FIG. 6) that provides electricalstimulation energy in the form of a pulsed electrical waveform to theelectrode array 26 in accordance with a set of stimulation parametersprogrammed into the IPG 14. Such stimulation parameters may compriseelectrode combinations, which define the electrodes that are activatedas anodes (positive), cathodes (negative), and turned off (zero),percentage of stimulation energy assigned to each electrode(fractionalized electrode configurations), and electrical pulseparameters, which define the pulse amplitude (measured in milliamps orvolts depending on whether the IPG 14 supplies constant current orconstant voltage to the electrode array 26), pulse width (measured inmicroseconds), pulse rate (measured in pulses per second), and burstrate (measured as the stimulation on duration X and stimulation offduration Y).

Electrical stimulation will occur between two (or more) activatedelectrodes, one of which may be the IPG case 44. Stimulation energy maybe transmitted to the tissue in a monopolar or multipolar (e.g.,bipolar, tripolar, etc.) fashion. Monopolar stimulation occurs when aselected one of the lead electrodes 26 is activated along with the case44 of the IPG 14, so that stimulation energy is transmitted between theselected electrode 26 and case 44. Bipolar stimulation occurs when twoof the lead electrodes 26 are activated as anode and cathode, so thatstimulation energy is transmitted between the selected electrodes 26.For example, an electrode on one lead 12 may be activated as an anode atthe same time that an electrode on the same lead or another lead 12 isactivated as a cathode. Tripolar stimulation occurs when three of thelead electrodes 26 are activated, two as anodes and the remaining one asa cathode, or two as cathodes and the remaining one as an anode. Forexample, two electrodes on one lead 12 may be activated as anodes at thesame time that an electrode on another lead 12 is activated as acathode.

The stimulation energy may be delivered between electrodes as monophasicelectrical energy or multiphasic electrical energy. Monophasicelectrical energy includes a series of pulses that are either allpositive (anodic) or all negative (cathodic). Multiphasic electricalenergy includes a series of pulses that alternate between positive andnegative. For example, multiphasic electrical energy may include aseries of biphasic pulses, with each biphasic pulse including a cathodic(negative) stimulation pulse and an anodic (positive) recharge pulsethat is generated after the stimulation pulse to prevent direct currentcharge transfer through the tissue, thereby avoiding electrodedegradation and cell trauma. That is, charge is conveyed through theelectrode-tissue interface via current at an electrode during astimulation period (the length of the stimulation pulse), and thenpulled back off the electrode-tissue interface via an oppositelypolarized current at the same electrode during a recharge period (thelength of the recharge pulse).

Referring to FIGS. 5 and 6 which show opposing internal sides of case44, in performing the above-described stimulation energy generationfunction, the IPG 14 comprises multiple electronic components, includingan electronic substrate assembly 50 and a battery 52 contained withinthe case 44, and a flex circuit 140 (see FIGS. 13A and 13B) coupled tothe electronic substrate assembly 50. The flex circuit 140 serves tocouple the electronic substrate assembly 50 to the electronic componentsin the header 46, which will be discussed in further detail below. Theelectronic substrate assembly 50 includes a printed circuit board (PCB)54 to which the previously described pulse generation circuitry 48 ismounted in the form of microprocessors, integrated circuits, capacitors,and other electronic components. The electronic substrate assembly 50further comprises a telemetry coil 56, a charging coil 58, andtelemetry/charging circuitry 60 mounted to the PCB 54. While a portionof the electronic components of the IPG 14 will be described in furtherdetail below, additional details of the IPG 14 and electrical componentsare disclosed in U.S. Pat. No. 6,516,227, which was previouslyincorporated herein.

The telemetry coil 56 and charging coil 58 are positioned on opposingsides of the PCB 54. Significantly, as shown in FIGS. 7 and 8, theelectronic substrate assembly 50 further comprises a spacer 62 on whichthe telemetry coil 56 is positioned to space the telemetry coil 56 adistance Dt away from the PCB 54. In the illustrated embodiment, thespacer 62 is a bobbin 62. The bobbin 62 has a main body 64 and an outerflange 66 extending around the periphery of the main body 64 on whichthe telemetry coil 56 sits, such that the coil 56 is wound around themain body 64 in a shape corresponding to that of the main body 64. Here,the telemetry coil 56 and the main body 64 of the bobbin 62 have aD-shaped configuration for encompassing a wide area in the case 44 toimprove coupling, and hence the reliability of data transfer, betweenthe telemetry coil 56 and the RC 16. In addition to maintaining thetelemetry coil 56 a distance away from the PCB 54, the bobbin 62 isbeneficial for manufacture, as the bobbin 62 provides a base on which toshape the telemetry coil 56, creating a more consistent design thanfreeform winding of the telemetry coil 56.

A number of pins 68, 70 are affixed to the bobbin for coupling thetelemetry coil 56 to the PCB 54. In the illustrated embodiment, thebobbin 62 has three holes 72 extending through the main body 64 of thebobbin 62 for receiving three pins 68, 70. In this embodiment, two ofthe pins 68 electrically connect the telemetry coil 56 to the PCB 54,and in particular, one pin 68 connects the ground port of the telemetrycoil 56, and the other pin connects the signal port of the telemetrycoil 56. The third pin 70 mechanically connects the telemetry coil 56 tothe PCB 54. In the illustrated embodiment, the two holes 72 forreceiving the two electrical pins 68 are located on one side of the mainbody 64 of the bobbin 62, and the one hole 72 for receiving themechanical pin 70 is located on an opposing side of the main body 64 ofthe bobbin 62. The pins 68, 70 may be secured in the holes 72 by weldingor other suitable means. In this manner, the pins 68, 70 facilitatesecure, accurate placement of the telemetry coil 56 relative to the PCB54, while the two pins 68 also provide an electrical connection betweenthe telemetry coil 56 and the PCB 54. In other embodiments, only one pinmay be used to electrically connect the telemetry coil 56 to the PCB 54,or more pins may be used to electrically and/or mechanically connect thetelemetry coil 56 to the PCB 54.

Notably, many typical IPGs contain a charging coil in the case and atelemetry coil in the header. In the illustrated embodiment, however,positioning both the charging coil 58 and the telemetry coil 56 in thecase 44 allows more room in the header 46 for other electroniccomponents. Additionally, positioning the telemetry coil 56 in the case44 eliminates the need for a feedthrough that connects the electronicsubstrate assembly 50 with the telemetry coil 56, as opposed to when atelemetry coil is in the header.

To realize potential effects associated with positioning both thetelemetry coil 56 and charging coil 58 in the case, it is helpful tonote the operation of the coils 56, 58. Regarding the telemetry coil 56,wireless data telemetry between the RC 16 and the IPG 14 occurs viainductive coupling, for example, magnetic inductive coupling. Thiscoupling occurs between the telemetry coil 56 in the IPG 14 and acorresponding external coil (not shown) in the RC 16. When data is sentfrom the RC 16 to the IPG 14, the external coil in the RC 16 isenergized with an alternating current (AC). This energizing of theexternal coil to transfer data can occur using a Frequency Shift Keying(FSK) protocol, for example, in which digital data bits in a stream arerepresented by different frequencies, as disclosed in U.S. patentapplication Ser. No. 11/780,369, which is incorporated herein byreference. Energizing the external coil with these frequencies producesa magnetic field, which in turn induces a voltage in the telemetry coil56 in the IPG 14, producing a corresponding current signal when provideda closed loop path. This voltage and/or current signal can then bedemodulated to recover the original data. Transmitting data in thereverse, from the telemetry coil 56 to the external coil, occurs inessentially the same manner.

Regarding the charging coil 58, when power is to be transmitted from theexternal charger 22 to the IPG 14, the charging coil 58 is energizedwith an alternating current (AC). Such energizing is generally of aconstant frequency and may be of a larger magnitude than that usedduring data transfer with the telemetry coil 56, but the basic operationis similar. The IPG 14 can also communicate back to the external charger22 by modulating the impedance of the charging coil 58. This change inimpedance is reflected back to the external charger 22, whichdemodulates the reflection to recover the transmitted data. This meansof transmitting data from the IPG 14 to the external charger 22 is knownas Load Shift Keying (LSK) and is useful to communicate data relevantduring charging of the battery 52 in the IPG 14, such as the capacity ofthe battery 52, extent of charging completed, and other chargingvariables. LSK communication between an IPG and external charger isfurther detailed in U.S. patent application Ser. No. 12/354,406, whichis incorporated herein by reference.

One possible issue that may arise with positioning both the telemetrycoil 56 and the charging coil 58 in the case 44 is that the mutualinductance of the coils 56, 58 may interfere with each other if bothcoils 56, 58 are receiving and transmitting data at the same time. Onemethod of addressing this is to include decoupling circuitry (not shown)for decoupling the charging coil 58 from the charging circuitry 60during periods of telemetry between the IPG 14 and the RC 16. Thedecoupling circuitry may be activated based on one or more operatingfactors, for example, when the telemetry coil 56 is sending or receivingdata to/from the RC 16, or when the charging circuitry 60 detects nocharging alternating current for the charging coil 58 to receive.

In another method, the LSK data signal is used to transmit serial datato the external charger 22 during charging, as is typical, and is alsoused as a control signal to reduce loading of the telemetry coil 56during data telemetry between the IPG 14 and the RC 16. Using thepreexisting LSK circuitry in this method requires no change in telemetrycircuitry other than to program the IPG 14 circuitry to assert LSK dataduring periods of data telemetry. Thus, the enhanced circuitry improvesreliability of telemetry between the RC 16 and the telemetry coil 56without substantial circuitry changes. Additional information regardingthe enhanced circuitry is detailed in application Ser. No. 12/616,178,filed Nov. 11, 2009, which is incorporated herein by reference.

The bobbin 62 also provides operational benefits with positioning thetelemetry coil 56 and the charging coil 58 in the case 44. For example,the bobbin 62 lessens the interference between the coils 56, 58 byincreasing the distance between the telemetry coil 56 and the chargingcoil 58, as described above. Additionally, the bobbin 62 places thetelemetry coil 56 in closer proximity to the case 44 to optimizetelemetry using resistance from the case 44. To illustrate, thetelemetry coil 56 may communicate on a seven-band frequency that isachieved by attaining a loss in transmission from resistance, e.g.,resistance from adjacent material. In prior embodiments wherein thetelemetry coil is positioned in the header, the header provides theresistance needed to obtain the ideal frequency. In the presentembodiment, in positioning the telemetry coil 56 closer to the case 44,the case 44 provides the resistance needed to create the desiredseven-band frequency for telemetry coil 56 transmission.

As mentioned above, the flex circuit 140 serves to couple the electronicsubstrate assembly 50 to the electronic components in the header 46. Inparticular, the flex circuit 140 is coupled to the PCB 54 and also tofeedthrough pins, described in further detail below, that in turn arecoupled to lead extensions 24 received in the header 46. As the flexcircuit 140 is a flexible metallic component (see e.g., FIGS. 13A and13B), the flex circuit 140 serves as an interface between the electronicsubstrate assembly 50 and the electronic components in the header 46 toprovide an electrical coupling function along with the ability to bebent in a suitable configuration to accommodate the size and structureof the IPG 14.

Coupling the flex circuit 140 to the PCB 54 eliminates the need forsoldering an additional plate to the PCB 54, making manufacture moreefficient and eliminating related quality issues that may otherwisearise. In some embodiments, the flex circuit 140 may be permanentlycoupled to the PCB 54, for example, by soldering, laser-welding,applying conductive epoxy or similar adhesive, or crimping. In otherembodiments, the flex circuit 140 may be detachably coupled to the PCB54, for example, by edge connectors such as zero insertion forceconnectors, snap-fit mechanisms, friction-fit mechanisms, and fastenerssuch as screws. In one embodiment, the substrate of the flex circuit 140is composed primarily of polyamide, which may be the same material fromwhich the PCB 54 is primarily composed. Other materials may also be usedfor the substrate of the flex circuit 140.

As mentioned above, the electronic components within the case 44 areelectrically coupled to the electrodes 26 via lead extensions 24received in the header 46, as shown in FIG. 4. Referring to FIGS. 4 and9, the header 46 includes: a shell 76 coupled to the case 44; aplurality of ports 78; a retainer 80; one or more connector assemblies82 positioned in the retainer 80; a corresponding number of connectorblocks 84 positioned in the retainer 80; one or more septums 86; and aplurality of strain relief members 88.

The shell 76 is formed using any suitable process, such as casting,molding, and the like, and is composed of a rigid material that does notinterfere with the electrical functions of the IPG 14, such asthermoset. The plurality of ports 78 extend through the shell 76 and areconfigured for receiving the lead extensions 24. Preferably, the numberof ports 78 corresponds to the number of lead extensions 24. Forexample, in the illustrated embodiment, there are four lead extensions24 and four ports 78. The header ports 78 are also aligned with retainerports 90, such that the lead extensions 24 are received in the headerports 78 and then in the retainer 80 through the retainer ports 90. Theretainer ports 90 (in this illustrated embodiment, four ports) are inturn aligned with the connector assemblies 82, such that the leadextensions 24 are received through the retainer ports 90 and then withinthe connector assemblies 82.

As shown in FIGS. 9 and 10, the retainer 80 receives the connectorassemblies 82 in corresponding retainer channels 92 that hold eachrespective connector assembly 82 in position. The retainer 80 ispreferably composed of a rigid material, e.g., thermoplastic, such thatthe connector assemblies 82 can be affixed relative to each other. Inone embodiment, the connector assemblies 82 are releasably disposed inthe retainer 80 in a suitable manner, such as with an interference fit,snap connection, binders, or other suitable mechanisms. Partitions 94 inthe retainer 80 keep the connector assemblies 82 separated to minimizeinterference.

The connector assemblies 82 receive and make electrical contact with thelead extensions 24. Each connector assembly 82 has a housing 96, ahollow center region 98 extending between a proximal end 100 and adistal end 102 of the housing 96, a plurality of openings 104transversely formed through the wall of the housing 96, and a pluralityof connector contacts 106 located within the hollow center region 98. Inthe illustrated embodiment, there are four connector assemblies 82aligned in a 2×2 configuration to make efficient use of space.Specifically, there are two upper assemblies 82 and two lower assemblies82, wherein the two lower assemblies 82 are designated as being closerto the case 44 than the two upper assemblies 82. Other embodiments mayinclude one assembly 82, or two assemblies 82 or more arranged in amanner suited to the configuration of the IPG 14. Suitable materials forthe housing 96 include, for example, silicone and polyurethane, andmultiple materials may be included. Each lead extension 24 is receivedthrough the distal end 102 of the respective housing 96 into therespective hollow center region 98.

The openings 104 in the housing 96 extend from an outer surface of thehousing 96 to the hollow center region 98. Preferably, the housingopenings 104 are linearly aligned along a side surface of the housing96. Each opening 104 provides access to a corresponding connectorcontact 106 within the housing 96. The connector contacts 106 areelectrically coupled to the electronic substrate assembly 50 in the case44 by a plurality of feedthrough pins, which are explained below ingreater detail.

When the lead extensions 24 are received in the connector assemblies 82,the connector contacts 106 electrically couple with terminals 108disposed on the lead extensions 24. The terminals 108 are in turncoupled to the lead electrodes 26 with conductive wires (not shown).Preferably, the number and spacing of the connector contacts 106 in eachconnector assembly 82 correspond to the number and spacing of theterminals 108 on each lead extension 24 to optimize coupling. In theillustrated embodiment, each of the four connector assemblies 82 haseight contacts 106, and each of the four lead extensions 24 has eightterminals 108. In this manner, when a lead extension 24 is received inthe hollow center region 98 of the connector assembly 82, each connectorcontact 106 electrically couples to a corresponding terminal 108 on thelead extension 24. This results in coupling between the electronicsubstrate assembly 50, which is coupled to the connector contacts 106 bythe flex circuit 140 and the feedthrough pins, and the electrodes 26,which are coupled to the terminals 108.

The retainer 80 has a number of end stops 110 each located at theproximal ends 100 of the housings 96 of the connector assemblies 82. Theend stops 110 are typically formed of a compressible material, such assilicone, and may be shaped as a block or alternatively have a curvedbowl-shaped configuration. The end stops 110 help to set the pitch forplacement of the connector contacts 106 during manufacture, for example,during precision-based processes such as laser soldering, to preventirregular placement of the connector assemblies 82 that would lead toincreased expense and quality issues. Also, during operation of the IPG14, the end stops 110 help limit movement of the connector assemblies 82to optimize transmission of electrical pulses from the connectorassemblies 82 to the lead electrodes 26. Additional details regardingsetting of pitch and use of end stops for connector assemblies arefurther described in U.S. Provisional Patent Application No. 61/378,613,filed Aug. 31, 2010, and U.S. Pat. No. 7,244,150, which are incorporatedherein by reference.

The connector blocks 84 are located at the distal end 102 of the housing96 and may also be coupled to the housing 96 and/or a wall of theretainer 96. In the illustrated embodiment featuring the 2×2 connectorassembly configuration, there are two upper connector blocks 84 adjacentthe two upper assemblies 82 and two lower connector blocks 84 adjacentthe lower assemblies 82. Each connector block 84 defines a port 112aligned with the hollow center region 98 for receiving a lead extension24. Each connector block 84 also has an aperture 114 on a side of theconnector block 84 through which a fastener 116, such as a setscrew orpin, is inserted and secured against the lead extension 24 receivedtherein. This helps to prevent undesirable detachment of the leadextensions 24 from the IPG 14 and to optimize electrical couplingbetween the lead terminals 108 and connector contacts 106.

The septums 86 have one or more slots 118 aligned with the connectorblock apertures 114 for receiving a fastening tool to secure thefastener 116 in each aperture 114. The septums 86 are positionedadjacent to, and may also be coupled to, the connector blocks 84. In theillustrated embodiment, two septums 86 are positioned on opposing sidesof the header 46, wherein each septum 86 is adjacent to two connectorblocks 84. Each septum 86 has an outer block 120 and an inner block 122,as shown in FIG. 10B, wherein the outer block 120 frames the inner block122, as shown in FIG. 10A. The blocks 120, 122 are composed of acompressible material, such as silicone. The demarcation between theblocks 120, 122 forms the slots 118 for receiving the fastening tool.For example, the upper edge of the inner block 122 forms an upper slot118 with the outer block 120, and the lower edge of the inner block 122forms a lower slot 118 with the outer block 120. Additionally, as shownin FIG. 10C, the upper slot 118 in each septum 86 is adjacent to theaperture 114 in each upper connector block 84, and the lower slot 118 ineach septum 86 is adjacent to the aperture 114 in the lower connectorblock 84.

Notably, in other devices wherein a septum only includes one block, theblock is typically pierced with a knife to create the slot for receivingthe fastening tool. However, this often results in coring of thematerial, wherein the cored material hinders insertion of the fastener.Additionally, silicone can demonstrate a tendency to “self-heal,” suchthat a slot formed by piercing a silicone block could close at leastpartially over time. However, by implementing two silicone blocks thatare pushed together, as in the illustrated embodiment, the tendency toself-heal is mitigated, and the slot remains intact.

Each septum 86 is positioned in an opening 124 formed through a surfaceof the header 46 (see FIG. 4), wherein edges of the opening 124 extendover the space underneath to form a frame 126, and the septum 86 ispositioned under the frame 126. In typical manufacturing practices, theseptum is pushed from outside the header into an opening in the header.However, this often results in the septum becoming loose and beingexpelled from the header. In the present embodiment, however, the septum86 is pushed into the opening 124 from inside the header 46, such thatthe frame 126 edges extending over the opening 124 prevent the septum 86from moving outside the opening 124. An adhesive, such as epoxy, is alsoapplied to adhere the septum 86 to the header 46, such that bothmechanical and adhesive elements hold the septum 86 in place. Additionaldetails regarding the connector assemblies and the components associatedtherewith are found in U.S. Provisional Patent Application No.61/378,613, filed Aug. 31, 2010, U.S. Pat. No. 7,244,150, and U.S.patent application Ser. No. 11/532,844, which are incorporated herein byreference.

The strain relief members 88 in the header 46 extend between each of theretainer ports 90 and the header ports 78. In the illustratedembodiment, there are four strain relief members 88 that correspond withthe 2×2 configuration of the connector assemblies 82, such that thereare two upper and two lower strain relief members 88. The strain reliefmembers 88 are formed as annular seals that help to prevent currentleakage outside the header 46 and to hold the lead extensions 24 inposition when inserted in the connector assemblies 82 while preventingdamage to the lead extensions 24. To correspond with the curvedformation of the header 46, the lower strain relief members 88 have alonger length than the upper strain relief members 88. This is becausethere is more space between the distal end 102 of the lower connectorassembly 82 and retainer port 90 and the corresponding header port 78than between the upper connector assembly 82 and retainer port 90 andthe corresponding header port 78.

In the illustrated embodiment, the header 46 also features a suture hole128 that extends between opposing sides of the header 46. To illustrate,a suture needle can go through suture hole 128 by entering one side ofthe header 46 and exiting on the other side. A clinician implanting theIPG 14 may thus use a suture needle with the suture hole 128 to affixthe IPG 14 to bodily tissue to help hold the IPG 14 in place. Each sideof the suture hole 128 is surrounded by a divot 130 in an outer surfaceof the header 46. The divot 130 is cut into the outer surface of theheader 46 and has a plurality of side surfaces 132, each side surface132 preferably angled less than 90 degrees from the outer surface of theheader 46, and a bottom surface 134 where the suture hole 128 ispositioned. The divot 130 and its configuration allow for ease inaccessing the header 46 with a suture needle, particularly a curvedsuture needle, to affix the IPG 14 to bodily tissue.

Referring to FIGS. 11-13B, a feedthrough assembly 136 electricallycouples the electronic substrate assembly 50 with the connectorassemblies 82. The feedthrough assembly 136 includes a plurality offeedthrough pins 138, a metal flange 142 defining a well 144, and one ormore ceramic plates 146 positioned in the well 144.

The feedthrough pins 138 are formed of 10 mL wire composed of 90/10platinum/iridium. In other feedthrough assemblies, the pins are composedof 80/20 platinum/iridium, however, this is less ductile and lesscompatible with soldering processes during manufacture. Preferably, thenumber of feedthrough pins 138 corresponds to the number of connectorcontacts 106 in the connector assemblies 82. In the illustratedembodiment, there are thirty-two feedthrough pins 138. The feedthroughpins 138 are coupled to the PCB 54 and extend through the case 44 andheader 46 to the connector assemblies 82, where the pins 138 are coupledto the connector contacts 106. The feedthrough pins 138 may be coupledto the connector contacts 106 by any suitable method including, forexample, welding, soldering, and the like. Notably, the feedthrough pins138 are sufficiently long to reach the connector contacts 106 withoutrequiring an additional wire to be soldered to each pin 136. Thiseliminates the need for additional manufacturing steps, thus limitingproduction costs and quality issues that would otherwise arise.

As mentioned above, the feedthrough pins 138 are each coupled to theflex circuit 140, which may be achieved in various manners. In theillustrated embodiment, each of the feedthrough pins 138 is inserted ina corresponding hole 148 in the flex circuit 140 (see FIG. 13A). Toinsert the feedthrough pins 138 through the flex circuit 140 duringmanufacture, the flex circuit 140 is initially flat, wherein each of thefeedthrough pins 138 is inserted through the corresponding hole 148.Using laser soldering, gold braze is applied on the underside of eachhole 148 around each pin 138 and seeps through the holes 148 to seal thepins 138 in the holes 148. This provides a metallurgical adhesive andelectrical connection, which may be advantageous over other sealantsthat only serve as an adhesive. Conductive epoxy may also be used toseal the pins 138 in the holes 148. The flex circuit 140 is then bentinto a curved configuration to suitably fit in the IPG 14 and to orientthe pins 138 upward for insertion through the header 46.

In another embodiment, the feedthrough pins 138 are attached to an edgeof the flex circuit 140, for example, by laser-soldering or with aconductive epoxy. In another embodiment, a portion of the pins 138 areattached to an edge of the flex circuit 140, and the remaining pins areinserted through holes 148 in the flex circuit 140.

In entering the header 46, the feedthrough pins 138 extend through themetal flange 142, which is located at the base of the header 46. Themetal flange 142 is composed of a biocompatible material, such astitanium. As mentioned above, the metal flange 142 defines the well 144,which is occupied by the ceramic plates 146. The ceramic plates 146 arefused to the metal flange 142 with gold braze. In the illustratedembodiment, two ceramic plates 146 are positioned adjacent each other inthe well 144. Alternative embodiments may consist of only one ceramicplate 146 that occupies the well 144. The ceramic plates 146 have anumber of holes 150 corresponding to the number of feedthrough pins 138,such that each pin 138 extends through one corresponding hole 150. Thepins 138 are fused to the ceramic plates 146 with gold braze that isapplied on the underside of the plates 146 and seeps through the holes150 to cover the pins 138 along the length of the holes 150.

The ceramic plates 146 have a lower coefficient of expansion than thetitanium of the metal flange 142, such that when the components areheated to extremely high temperatures during manufacture, the ceramicplates 146 expand less than the flange 142. As a result, less of thegold braze can seep from between the metal flange 142 and the ceramicplates 146. Also, since the holes 150 receiving the pins 138 in theplates 146 do not widen significantly, the gold braze securing the pins138 is substantially prevented from seeping through the holes 150, thusserving to stabilize the pins 138.

To isolate the feedthrough pins 138 from each other and limit electricalconnectivity in between, and to further provide protection to the pins138 in the transition between the case 44 and the header 46, each of thefeedthrough pins 138 is covered with a silicone tube 152 from the baseof the ceramic plates 146 up to the point at which the feedthrough pins138 couple to the connector contacts 106 (see FIG. 5). Additionally, thewell 144 is filled with silicone (not shown) to provide furtherisolation between the pins 138.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed is:
 1. A tissue stimulation system, comprising: at leastone implantable neurostimulation lead; and an implantableneurostimulator comprising a header having at least one connectorassembly configured for respectively receiving the at least oneneurostimulation lead, a circuit board having programming circuitry, aflex circuit coupled between the at least one connector assembly and thecircuit board, and a case to which the header is coupled, the caseincluding a hermetically sealed compartment enclosing the circuit boardand the flex circuit.
 2. The tissue stimulation system of claim 1,wherein the flex circuit is coupled to the circuit board by soldering.3. The tissue stimulation system of claim 1, wherein the flex circuit iscoupled to the circuit board with conductive epoxy.
 4. The tissuestimulation system of claim 1, further comprising a feedthrough assemblycoupled between the flex circuit and the at least one connectorassembly, the feedthrough assembly comprising a plurality of pinscoupled to the flex circuit that electrically couple the flex circuit tothe at least one connector assembly.
 5. The tissue stimulation system ofclaim 4, wherein the plurality of pins are coupled to the flex circuitwith gold braze.
 6. The tissue stimulation system of claim 4, whereinthe plurality of pins are coupled to the flex circuit with conductiveepoxy.
 7. The tissue stimulation system of claim 4, wherein one or moreof the plurality of pins traverse through one or more holes in the flexcircuit.
 8. The tissue stimulation system of claim 4, wherein thefeedthrough assembly further comprises a metal flange forming a wellcontaining an insulative material, and the pins extend from the flexcircuit through the insulative material.
 9. The tissue stimulationsystem of claim 8, wherein the pins extend from the material to the atleast one connector assembly.
 10. The tissue stimulation system of claim9, wherein a portion of the pins extending from the material to the atleast one connector assembly is covered with silicone.
 11. The tissuestimulation system of claim 4, wherein the pins are composed of amaterial comprising Ti 90/10.
 12. The tissue stimulation system of claim4, wherein the at least one connector assembly comprises a plurality ofconnector contacts for electrically coupling with the neurostimulationlead, and the pins are electrically coupled to the connector contacts.13. The tissue stimulation system of claim 1, wherein the at least oneconnector assembly comprises a plurality of connector contacts.
 14. Thetissue stimulation system of claim 1, further comprising a suture holeextending between opposing sides of the header and surrounded by a divotformed in an outer surface of the header on each of the opposing sidesof the header.
 15. An implantable neurostimulator, comprising: at leastone connector assembly configured for receiving at least oneneurostimulation lead; a circuit board having programming circuitry; aflex circuit coupled between the at least one connector assembly and thecircuit board; and a case including a hermetically sealed compartmentcontaining the circuit board and the flex circuit.
 16. Theneurostimulator claim 15, wherein the flex circuit is coupled to thecircuit board by soldering.
 17. The neurostimulator of claim 15, whereinthe flex circuit is coupled to the circuit board with conductive epoxy.18. The neurostimulator of claim 15, further comprising a feedthroughassembly coupled between the flex circuit and the at least one connectorassembly, the feedthrough assembly comprising a plurality of pinscoupled to the flex circuit that electrically couple the flex circuit tothe at least one connector assembly.
 19. The neurostimulator of claim18, wherein the plurality of pins are coupled to the flex circuit withgold braze.
 20. The neurostimulator of claim 18, wherein the pluralityof pins are coupled to the flex circuit with conductive epoxy.
 21. Theneurostimulator of claim 18, wherein one or more of the plurality ofpins traverse through one or more holes in the flex circuit.
 22. Theneurostimulator of claim 18, wherein the feedthrough assembly furthercomprises a metal flange forming a well containing an insulativematerial, and the pins extend from the flex circuit through theinsulative material.
 23. The neurostimulator of claim 22, wherein thepins extend from the material to the at least one connector assembly.24. The neurostimulator of claim 23, wherein a portion of the pinsextending from the material to the at least one connector assembly iscovered with silicone.
 25. The neurostimulator of claim 18, wherein thepins are composed of a material comprising Ti 90/10.
 26. Theneurostimulator of claim 18, wherein the at least one connector assemblycomprises a plurality of connector contacts, and the pins areelectrically coupled to the connector contacts.
 27. The neurostimulatorof claim 15, wherein the at least one connector assembly comprises aplurality of connector contacts.
 28. The neurostimulator of claim 15,further comprising a shell containing the at least one connectorassembly.
 29. The neurostimulator of claim 28, wherein the shellcomprises a suture hole extending between opposing sides of the shelland surrounded by a divot formed in an outer surface of the shell oneach of the opposing sides of the shell.
 30. The neurostimulator ofclaim 15, further comprising a header containing the at least oneconnector assembly, wherein the header is coupled to the case.